Circuit breakers are used to protect electrical systems in case of overcurrent conditions which can be caused by, for example, short circuits or broken loads. Traditionally, circuit breakers were mechanical switches that would open upon detection of an overcurrent condition. Recently, in place of the traditional mechanical switches, electronic devices such as metal-oxide-semiconductor field-effect transistor (MOSFET) power switches have been implemented.
Multiple circuit breakers are often implemented to accommodate multiple loads. They can either be used as stand-alone circuit breakers, or in parallel to form a higher tolerance breaker. If used in parallel, the circuit breakers must share current between one another. Ideally, for example, two five amp circuit breakers would combine to form a ten amp circuit breaker when connected in parallel. In practice, however, unequal current sharing due to internal tolerancing often results in one breaker that draws more current than the other, and thus trips earlier. This leads to the parallel circuit breakers providing a higher than desired tolerance.